Narrow.lua

local Narrow, parent = torch.class('nn.Narrow', 'nn.Module')

function Narrow:__init(dimension,offset,length)
   parent.__init(self)
   self.dimension=dimension
   self.index=offset
   self.length=length or 1
   if not dimension or not offset then
      error('nn.Narrow(dimension, offset, length)')
   end
end

function Narrow:updateOutput(input)
   local output=input:narrow(self.dimension,self.index,self.length);
   self.output:resizeAs(output)
   return self.output:copy(output)
end

function Narrow:updateGradInput(input, gradOutput)
   self.gradInput:resizeAs(input)  
   self.gradInput:zero();
   self.gradInput:narrow(self.dimension,self.index,self.length):copy(gradOutput)
   return self.gradInput
end